Dual Key Encryption in Python
Dual key encryption, also known as public/private key cryptography, is a core concept in modern data security. It is widely used in secure communications, digital certificates, and encrypted web applications. In this tutorial, you will learn how public and private key encryption works in Python, why it is classified as asymmetric encryption, and how dual keys are used to securely encrypt and decrypt data.
This explanation is designed for tertiary-level students and beginners who want a clear, practical understanding of cryptography concepts without unnecessary complexity.
What Is Dual Key (Public/Private Key) Encryption? | Explanation for Python Kids
Dual key encryption is an encryption method that uses two mathematically related keys:
- A public key, which is shared openly and used to encrypt data
- A private key, which is kept secret and used to decrypt data
This approach is formally known as public key cryptography or asymmetric encryption. Unlike symmetric encryption, where the same key is used for both encryption and decryption, dual key encryption ensures that encrypted data can only be decrypted by the intended recipient.
Why Asymmetric Encryption Is Important | Explanation for Python Kids
Asymmetric encryption solves a major problem in secure communication: key sharing. Since the public key can be distributed freely, there is no need to transmit a secret key over an insecure channel.
Key advantages include:
- Improved security for data transmission
- Safe communication over public networks
- Strong authentication mechanisms
- Foundation for HTTPS, SSL/TLS, and digital signatures
Because of these benefits, public/private key encryption is commonly used in web applications, secure messaging systems, and online banking platforms.
How Dual Key Encryption Works (Step by Step) | Explanation for Python Kids
The dual key encryption process follows a logical sequence:
- A key pair is generated (public key and private key)
- The sender encrypts data using the public key
- The encrypted message is transmitted
- The recipient decrypts the message using the private key
Only the matching private key can decrypt the data, even though the public key is visible to everyone. This is what makes asymmetric cryptography secure.
Python Example: Public and Private Key Encryption
In Python, asymmetric encryption can be implemented using cryptographic libraries or the Web Crypto API. The general workflow remains the same regardless of the specific implementation.
A typical Python public/private key encryption process includes:
- Generating an RSA key pair
- Encrypting data with the public key
- Decrypting encrypted data with the private key
This approach allows Python applications to securely handle sensitive information such as passwords, tokens, and confidential messages.
The Mathematics of Public Key Encryption | Math Explanation for Python Kids
At its core, dual key encryption relies on the mathematical difficulty of factoring large numbers. Our Python RSA encryption tutorial focuses on the relationship between prime numbers and modular arithmetic. To generate a secure pair of keys, we follow a rigorous mathematical process:
- Prime Selection: Choosing two large prime numbers ( and ) to create a semi-prime modulus.
- LCM Calculation: Determining the Lowest Common Multiple of $(p-1)$ and $(q-1)$.
- Key Generation: Selecting a Public Key that is coprime to the LCM.
- The Inverse: Calculating the Private Key as the modular multiplicative inverse of the Public Key.
- Encrypt data: \([Unicode(data)]^{public\_key} % semi_prime = encoded_data;\)
- Decrypt data: \([encoded\_data]^{private\_key} % semi_prime = original data;\)
Implementing RSA Logic in Python
While many modern applications use the built-in WebCrypto API, writing a manual RSA implementation is the best way to grasp how ciphertext and plaintext interact.
Using Python's Long int capability, we can handle the large-scale integer calculations required for secure encryption. Below, we explore the Python code required to transform a standard Unicode string into an encrypted hexadecimal array, ensuring that only the holder of the private key can reverse the process.
Create a new Python module file;
Call it DualKeyEncryption.py
.
Type out the adjoining Python code for encrypting and decrypting a chunk of data
using a Public Key - Private Key pair.
By The Way: The encryption algorithm described in the above steps is called R.S.A. algorithm; and coming up with an algorithm that can factor very large semi primes into their prime factors in linear time is called the R.S.A. problem.
Also noteworthy is the fact that there are other ways of implementing an open-lock-only encryption algorithm; like the Logarithm Encryption, e.t.c.
Note: int (long) in Python is boundless in size so no BigIntegers are required.
The Python code module for finding LCM
is from the Primary Category.
Just make a copy of it into the current folder (project).
Why Use RSA in Python?
- Educational Value: Great for learning cryptography concepts.
- Practical Applications: Secure login systems, encrypted messaging, and digital signatures.
- Flexibility: Python runs everywhere — windows, linux, and android.
Dual Key Encryption vs Symmetric Encryption | Explanation for Python Kids
It is important to distinguish between symmetric encryption and dual key encryption:
| Feature | Symmetric Encryption | Dual Key Encryption |
|---|---|---|
| Number of keys | One shared key | Two separate keys |
| Security | Lower for key exchange | Higher for communication |
| Speed | Faster | Slower |
| Common use | Data storage | Secure communication |
In practice, many systems use both methods together, combining the speed of symmetric encryption with the security of asymmetric encryption.
Common Uses of Public/Private Key Cryptography | Explanation for Python Kids
Public and private key encryption is used in many real-world applications, including:
- Secure web communication (HTTPS)
- Digital certificates and authentication
- Secure email systems
- Encrypted file sharing
- Secure API communication
Understanding dual key encryption in Python provides a strong foundation for learning advanced security and cryptography topics.
Key Takeaways from the Python Dual Key Encryption Algorithm
- Dual key encryption uses a public key for encryption and a private key for decryption
- It is also known as public/private key cryptography or asymmetric encryption
- Python supports public key encryption through cryptographic APIs and libraries
- This method is essential for secure communication on the web
Summary: Python Dual Key Encryption Algorithm
By understanding RSA encryption in Python, you gain insight into how modern cryptography protects sensitive information. Whether you're a student exploring modular arithmetic or a developer implementing public/private key cryptography, this tutorial provides the foundation you need.
Python Code for Dual Key Encryption - Module File
# define a class
class OpenEncryption:
def __init__(self, semi_p):
self.semi_prime = semi_p
##
# STEP VI:
##
def encodeWord(self, msg, key):
encryption = []
for i in range(len(msg)):
# get unicode of this character as x
x = ord(msg[i])
# use RSA to encrypt & save in base 16
encryption.append(hex(int(x**key % self.semi_prime))[2:])
return encryption
##
# STEP VII:
##
def decodeWord(self, code, key):
decryption = ""
for i in range(len(code)):
# use RSA to decrypt
c = int(code[i], 16)**key % self.semi_prime
decryption += chr(int(c))
return decryption
Python Code for Dual Key Encryption - Main Class
from DualKeyEncryption import OpenEncryption
##
# STEP I:
##
p1 = 101
p2 = 401
##
# STEP II:
##
semi_prime = p1 * p2
##
# STEP III:
##
from LCM import findLCM
l_c_m = findLCM([p1 - 1, p2 - 1])
lcm = int(l_c_m.getLCM())
##
# STEP IV:
##
# pick a random prime (public_key) that lies
# between 1 And LCM but Not a factor of LCM
public_key = 313
# find "public_key" complement - private_key - such that
# (public_key * private_key) % LCM = 1
# this involves some measure of trial And error
i = 1
while (lcm * i + 1) % public_key != 0:
i += 1
##
# STEP V:
##
private_key = int((i * lcm + 1) / public_key)
message = list("merry xmas")
go_secure = OpenEncryption(semi_prime)
encrypted = go_secure.encodeWord(message, public_key)
print("Message is '", ''.join(message), "';\nEncrypted version is ", encrypted)
decrypted = go_secure.decodeWord(encrypted, private_key)
print("\nDecrypted version is '", decrypted, "'.")